Question

I have implemented custom errors in my asp.net mvc application by following this article. What I have noticed is that if I go to http://www.mysite.com/some-non-existent-controller-and-action I get my 404 error page as expected. However, looking at what happens with firebug, I see that I get a 302 Found response for the non-existent page, which then redirects to my custom error page which then returns with a 404 (and displays the custom error page). Is this right? I don’t think the 302 that is first returned is very good especially from an SEO perspective, and that maybe I need to think again about how I have implemented this.

Answer 1

The best guide(i think) for handling 404s can be found in this answer. Basically there are multiple ways in which 404s can happen:

1. No route exists – matched by the catch all rule.
2. Matched route but not found a controller – for rules with dynamic controller names – {controller}/{action}/{parameter} rule.
3. Found route, but didn’t find action – handled through HandleUnknownAction override.
4. Found route and action but couldn’t convert parameters – matched by the catch all rule.

The linked answer basically sets up a controller that can be executed from any point in the code without rewriting the URL – which is what you want.

In addition, you should also think about handling unhandled exceptions and bad URLs (like the ones containing unsafe characters like angle brackets). I that particular case you have to rewrite the URL, otherwise you can’t render the response at all. These particular requests are kind of tricky, i blogged about that here.